Fuel injectors are required to deliver closely calibrated quantities of fuel in rapid succession under extreme conditions of pressure and temperature. Because of the great demands placed upon them, fuel injectors are typically complex and expensive to manufacture. The present invention utilizes the properties of electro-rheological fluids to minimize both the complexity and cost of fuel injectors, while at the same time, providing improved operation, fuel efficiency, and performance.
Various forms of compression operated fuel injectors have been developed. In the more recent of these prior art devices, the injection of fuel has been controlled electronically or by mechanical activation. Typically, these devices use solenoid valves to control the timing and the amount of fuel to be supplied. Examples of compression operated injectors include U.S. Pat. Nos. Re. 23,476 to French; Re. 29,978 and U.S. Pat. No. 3,926,169 to Leshner, et al; and U.S. Pat. No. 1,995,469 to Olsen. Electronic and mechanical fuel injectors typically require electro-magnetic or electronic apparatus to control the injection event. This equipment is complex and expensive.
It has been recognized for several decades that certain fluids respond to the influence of an electric potential by evidencing a rapid and pronounced increase in viscosity and an increased resistance to shear. Such electro-rheological or electroviscous fluids comprise slurries of finely divided hydrophilic solids in hydrophobic liquids. In the absence of an electric field, these fluids behave in a Newtonian fashion. But, when an electric field is applied, the fluids become proportionately more viscous as the potential of the electric field increases. In strong electric fields, these fluids can thicken into a solid. The electro-rheological phenomenon reverses when the electric potential is removed, and the material returns to its fluid state.
Electro-rheological fluids change their characteristics very rapidly when electric fields are applied or released, with typical response times being on the order of one millisecond. The ability of electro-rheological fluids to respond rapidly to electrical signals makes them well suited as elements in mechanical devices. Patents directed to compositions of electro-rheological fluids include U.S. Pat. Nos. 3,367,872; 3,047,507 and 4,033,892. Electro-rheological fluids have been extensively used in clutches as disclosed, for example, in U.S. Pat. Nos. 4,444,298 and 4,493,615, and more recently in dampening devices and hydraulic applications.
Until recently, the practical application of electro-rheological fluids was limited to low temperature environments due to the previously required presence of water in the electro-rheological fluid. In a high temperature environment, the water in the fluid would vaporize and lead to corrosion. This strictly limited the use of electro-rheological fluids toward low temperature applications on or near gasoline and diesel powered automobile and truck engines and the like. Recently, the temperature problem has been minimized with advances in electro-rheological fluid technology such as those disclosed in U.S. Pat. Nos. 4,744,914 and 4,772,407. Electro-rheological devices, because of their special nature, offer numerous advantages over mechanical valve control devices incorporating hydraulic, solenoid and cam operated action, such as that utilized in conventional fuel injectors.
Recently, an electro-rheological fuel injector was disclosed in U.S. Pat. No. 4,700,678 to Elliott. The fuel injector disclosed by Elliott is complicated and utilizes relatively large quantities of electro-rheological fluids. In addition, the injector disclosed in U.S. Pat. No. 4,700,678 has a tendency to accumulate dirt and debris. It also requires a complex by-pass mechanism for controlling the thrust of the injector and the duration of the injection event.
It would be desireable to have a simplified fuel injector which can utilize electro-rheological fluid to precisely meter an amount of fluid into an engine, and which improves over designs such as that disclosed by Elliott in U.S. Pat. No. 4,700,678.
It would further be desirable to have an electro-rheological fuel injector with valving which utilize novel electrode configurations, and which can more easily and more precisely meter quantities of fuel into the engine.
It is therefore an object of the present invention to provide an electro-rheological fuel injector which can be utilized to precisely meter and control the levels and amounts of fuel fed to an engine from a fuel injector and which can easily replace a conventional fuel injector, and which does not tend to accumulate dirt and debris.
It is a further object of the present invention to provide an electro-rheological fuel injector which can be constructed less expensively than standard fuel injectors and which can be utilized to precisely control the amount of thrust of a plunger member utilized in association with an electro-rheological fluid.
It is still a further object of the present invention to provide an electro-rheological fuel injector which can replace conventional fuel injectors in both automobile and diesel engines.
It is still a further object of the present invention to provide an electro-rheological fuel injector which utilizes novel valve mechanisms which control the timing and duration of an injection event.